I. Technical Field
The present invention relates to a cage for a constant velocity universal joint, and more particularly, to a cage for a constant velocity universal joint of a fixed type, which is used in a power transmission system in an automobile or various industrial machines and in which balls are used as rolling bodies.
II. Description of the Related Art
Generally, a constant velocity universal joint is provided with an outer joint member which has track grooves formed on an inner diameter side thereof, an inner joint member which has track grooves formed in an outer diameter side thereof, multiple balls which are interposed between the track grooves of the outer joint member and the track grooves of the inner joint member so as to transmit torque, and a cage which is interposed between the inner diameter surface of the outer joint member and the outer diameter surface of the inner joint member so as to hold the balls.
In the constant velocity universal joint as described above, the outer diameter surface and the inner diameter surface of the cage are brought into contact with the outer race as the outer joint member and an inner race as the inner joint member. Thus, by machining (machining of quenched steel) after a thermal curing process (quenching), the inner diameter surface and the outer diameter surface of the cage secure the dimensional accuracy and the surface roughness thereof (JP 2002-188653 A). As described in JP 2002-188653 A mentioned above, in the case of machining the cage after quenching, the cage is finished such that the surface roughness of the outer diameter surface and the inner diameter surface thereof is uniform over the entire region extending from one end side to the other end side thereof.